PRODUCT PORTFOLIO: Buyers' Guide - Colour digital & DI presses.(Buyers Guide)

There's a lot to consider before entering the digital colour market. Darryl Danielli looks at what's on offer.

Indigo launched its first e-Print digital press in '93. Since then, the short-run digital colour market has been one of the fastest growing sectors in the print industry. When you add to this the increasing popularity of direct imaging (DI) presses - which began in 1991 with the Heidelberg GTO DI, but which took off at Drupa 2000 when a plethora of manufacturers joined the DI fray - we haven't just entered the digital age, we're through the door and we've made ourselves at home.

Digital presses differ from DI presses; digitals are capable of some form of variable print, usually on a page-by-page, or a batch basis, without stopping the press to re-image or download a new job. Meanwhile, DI presses are offset presses equipped with some means of writing the image directly onto the cylinder or onto a plate mounted on the cylinder. Most DI presses are waterless - this avoids ink/water balance know-how of conventional offset printing and produces saleable sheets faster.

Some DI presses are slower than conventional offset presses, due to an internal cylinder configuration mounting two plates on a single cylinder to save money on imaging heads. MAN Roland's DICOweb DI web is interesting as it's the first DI press to image directly onto re-usable sleeves on the cylinder. Scrubbed between jobs, it exposes a new image and removes the need for plates altogether.

While DI presses can offer reduced costs in terms of makereadies (and perhaps also in consumables use, depending on the technology used) a makeready time is still involved, and therefore the minimum break-even run length is still a reality. For digital presses, this is not the case: run lengths as short as just a single copy can be produced economically, because there's no call for wash-ups, imaging time, or even any significant downtime between jobs. The press is able to run as fast, and change information on the page as often, as its RIP can drive it.

There are several different approaches to digital press technology, but in general all are characterised by the absence of a conventional printing plate, taking imaging data direct from a RIP linked to a workstation.

The most common technology for digital presses is electrophotographic.